High bit rate digital subscriber line: a copper bridge to thenetwork of the future

It is argued that the high bit rate digital subscriber line (HDSL), permitting low-cost 1.5 Mb/s copper access, will ease the transition to fiber access by accelerating the use of higher speed services. Copper will dominate over fiber customer access for at least the next ten years. During this period, the success of high-speed switched services will depend on the connectivity provided by both fiber and copper access. HDSL will initially be used to serve private-line DS 1, ISDN primary rate access, and digital loop carrier feeders. Later, the HDSL will be applied to switched services such as metropolitan area networks (MANs) and circuit switched DS1s     

The error performance of digital subscriber lines in the presenceof impulse noise

This paper describes the error performance of the ISDN basic access digital subscriber line (DSL), the high bit rate digital subscriber line (HDSL), and the asymmetric digital subscriber line (ADSL) in the presence of impulse noise. Results are found by using data from the 1986 NYNEX impulse noise survey in simulations. It is shown that a simple uncoded ADSL would have an order of magnitude more errored seconds than DSL and HDSL     

Implementation of a broadband integrated services hybrid network

The issues involved in the design of a broadband integrated services digital network (B-ISDN), that utilizes optical fibers in the subscriber loop, are considered. A hybrid scheme that provides integrated access to ISDN and broadband services by delivering voice/data signals in a digital format while using an analog format for full-motion video services to subscribers is proposed. The discussion covers planning for a B-ISDN, the system concept, implementation, the loop fiber network, subscriber equipment, and cost comparison and analysis     

Technology Aspects for System 12 Broadband ISDN

Although the enhancement of System 12, SEL's digital switching system, for ISDN services is virtually complete, further development work is being carried out to allow broadband switching for videophone services, videoconferencing, and the distribution of radio and television programs. This paper describes an appropriate approach to the evolution Of System 12 toward the broadband ISDN (B-ISDN), emphasizing the crosspoint and technology aspects of the broadband switch. Test results on a broadband switch VLSI circuit for 140 Mbit/s in a 2μm CMOS technology are presented.     

Network and System Architecture: The Integrated Approach to ISDN in the UT Line

The paper presents an approach to ISDN suitable both for a pilot service, to be carried out in the near future in Italy, and for long-term developments with a high degree of penetration of ISDN setvices. Integration of ISDN services in the digital telephone exchange "UT" has taken place at all levels: system architecture, subscriber access structure, circuit connecting network, transmission links, call processing, and 0 & M functions. We also describe a new protocol that facilitates the dialog between exchange modules and between different exchanges for the data service. It is suitable for implementing packet transit switches with low complexity, high throughput, and low transit time. A special peripheral-handling processor handles the most repetitive functions of the protocols both in the local exchange and in other parts of the network, while the exchange central processor performs the ISDN call-handling functions; the same peripheral processors and the same module processor are used for both ISDN and telephone services. Finally, the paper shows how this architecture can evolve to include new wide-band services and new techniques to implement high-capacity fast packet switches.     

Signaling System No. 7 ISDN User Part

The integrated services digital network (ISDN) user part of Signaling System No. 7 defines the signaling protocol which supports the establishment, supervision, and release of voice and nonvoice calls over circuit-switched connections between ISDN terminations of digital subscriber access lines. This paper gives an overview of the ISDN user part protocol, as defined in CCITT Recommendations Q.761-Q.766 [1], in terms of the signaling functions and procedures provided to support call and connection control in an ISDN, and in terms of the information elements and signaling messages that are used by the signaling functions in ISDN exchanges to communicate.     

Switching System Software Design for ISDN

The ISDN offers various services through multipurpose digital subscriber lines. The switching program for the ISDN should be so designed as to realize the control of various voice and nonvoice services and provide for developing service enhancement. To attain the goal, the ISDN services are classified hierarchically and each category is allocated to appropriate network nodes for implementation. As a result, the local switching program provides an out-slot subscriber line signaling capability and call connection with appropriate compatibility checking including a check for access capability to communications processing nodes. The switching program modules specific to analog services and those specific to digital services are separated to allow the use of the existing program file and to afford easy program design and maintenance. Remote-controlled switching is a suitable means for an economical introduction of the ISDN services to low traffic density areas. Special routing and reliability arrangements as well as the program structure for a remote-controlled switch are discussed.     

Design Philosophy and Hardware Implementation for Digital Subscriber Loops

This paper presents various requirements and configurations in the information network system (INS) NTT's version of the integrated services digital network (ISDN)- such as field trials, and technologies and equipment design of the digital subscriber loop using balanced wire pairs. The main aspects characterizing digital subscriber loops, are a customer access structure, a digital transmission system on existing subscriber loops, and customer interface. A configuration of two-wire digital subscriber loops with two customer access channels, which is adopted in the field trials, will be described. The time-shared two-wire digital transmission and power feeding methods on subscriber loops are discussed. The common mode rejection ratio (CMRR) is discussed in detail, since CMRR is one of the main factors which affects the transmission ability of balanced wire pairs. A proposed self-clocked four-wire customer interface utilizes time division multiplexing technique. The digital subscriber loop operates on a call-by-call basis for link establishment to avoid excessive power dissipations as well as to avoid impairments caused by crosstalk from other lines within a cable. Its design objectives and implementation are also discussed.     

基于V5的用户接入系统ISDN接入模块的设计与实现

介绍Ｖ５接入网用户接入系统的ＩＳＤＮ接入模块硬件和软件设计方案。这个方案具有系统配置灵活的特点。另外,此方案主要采用西门子公司的芯片组。     

Digital subscriber lines: network considerations for ISDN BasicAccess standard

The authors review digital subscriber line (DSL) technology features and the key technical factors that have driven the development of the technology. The application of DSL technology to network access and the relevant standards activities that provide a framework for developing DSL performance requirements are considered. The important aspects of the physical and operational characteristics of the US loop plant that influenced critical technology choices are reviewed with an emphasis on the physical characteristics of the embedded loop plant and considerations pertinent to the economic provisioning and operations for ISDN (integrated services digital network) Basic Access. A review of the essentials of DSL technology for ISDN Basic Access is presented     

Simulation of ADSL over ISDN on German subscriber lines

The shortcomings of the existing asymmetric digital subscriber line (ADSL) standard ANSI T1.413 for application with the integrated services digital network (ISDN) are explained. An ADSL system modified by increasing the high-pass cutoff frequency of the splitter to about 140 kHz and, therefore, moving also the pilots, has been simulated under noise conditions and the ISDN requirements of the German subscriber line network. The reach reduction due to ISDN compared with the “plain old telephone service” (POTS) application is shown to he between 10% and 15%. It is proposed to apply ISDN ADSL rather than POTS ADSL     

Object-oriented design of ISDN call-processing software

The development of object-oriented programming (OOP) software for a prototype switching system, including the DSS1 protocol on integrated services digital network (ISDN) subscriber signaling and the ISDN user part (ISUP) for network signaling, is discussed. The major goal of the project is to determine whether switching system software can be clearly structured by using the rules of OOP, and whether the use of OOP concepts leads to an improvement in productivity and quality for large software systems. The standard classes, application classes, class hierarchy, and layer model with the OOP project are described. The experiences in applying OOP for the development of switching system software are summarized     

An ISDN Subscriber Loop Transmission System Based on Echo Cancellation Technique

This paper proposes an ISDN subscriber loop transmission system based on an echo cancellation technique which fully supports the CCITT recommended basic interface for ISDN, i.e.,B + B + Dover metallic cables. System design considerations of cable loss, crosstalk, impulsive noise, and system requirements such as power feeding on a caLl-by-call basis are discussed, and a transmission system is proposed. The proposed system is characterized by the use of a new line code, named "modified biphase code." The use of this code with fixed line loss equalization and coherent detection achieves circuit simplification. A special adaptation algorithm is incorporated with the echo canceller that significantly reduces convergence time. Experimental results show satisfactory performance with respect to the residual echo and the bit error rate. Since the system requires only a simple nonadaptive circuit for analog portion, it is suitable for LSI implementation.     

Deployment of ATM subscriber line systems

A B-ISDN introductory scenario is described from the viewpoint of service, and a virtual-path (VP)-based access network architecture based on this scenario is discussed. In the access network each VP is dedicated to one service, such as a leased circuit, switched circuit, or video distribution. The concept and functions of a subscriber line terminal (SLT) to realize this capability are introduced. Asynchronous transfer mode (ATM) subscriber line system deployment and the main SLT functions are discussed     

A 3.3-V ISDN U-interface line driver with a new I/sub Q/-control circuit

In this work, we propose a new quiescent current (I/sub Q/) control circuit applicable to line drivers for digital subscriber line (DSL) applications. The line driver consists of preamplifier, error amplifiers, output transistors, and I/sub Q/ control circuits. A new method is proposed for controlling I/sub Q/ values in order to obtain high linearity performance. It also helps to determine the minimum off-current value of the class-AB output stage to reduce crossover distortion. The line driver is implemented for ISDN U-interface applications. It is fabricated in a 0.35-/spl mu/m CMOS technology for a single power supply voltage of 3.3 V, and a total harmonic distortion of less than -64 dB is achieved.     

Wide-band digital subscriber access with multidimensional blockmodulation and decision-feedback equalization

The author investigates the potential transmission performance of pair-wire subscriber lines at the higher rate of 800 kb/s, with particular reference to digital subscriber line transmission for ISDN (integrated services digital network) basic access. Block modulation schemes of 1-4 dimensions, at a rate of 2 bits per dimension, are considered. Time-division multiplexing is used to combine the multiple dimensions for transmission over a single-waveform channel, namely, the subscriber line. The channel noise is assumed to be additive and dominated by near-end crosstalk. MMSE (minimum mean-squared error) decision-feedback equalization is used to deal with the noise and the intersymbol interference. Using the theory developed, the potential performance of some simple lines is calculated. The coding gain of a multidimensional modulation scheme is found to be fully preserved after transmission if the equalizer is infinite in length. However, the gain realized can be much lower, or none at all, if the equalizer is only moderate in length. This latter phenomenon is due to the fact that the noise at the decision point is coloured, due to the inability of the equalizer to whiten it sufficiently     

Communications [technology analysis and forecast]

Several spectacular changes in the communications scene over the past few years will have a still stronger impact in 1997. Most obviously, the World Wide Web has been expanding. Showing a nice mixture of optimism and concern, the telecommunications establishment is mulling how best to exploit the Web commercially while deploying such packet-switched networks as the integrated services digital network (ISDN) and such subscriber access technologies as asymmetric digital subscriber line (ADSL) to keep the telecom infrastructure from being overwhelmed. Amid the competitive pressures generated by deregulation, telecom companies have more incentive than ever to squeeze as much performance as possible out of their existing infrastructure. Hence the attraction of local-access technologies like ADSL for boosting the capacity of installed copper subscriber loops, and long-haul technologies like wavelength division multiplexing (WDM) for boosting the capacity of installed optical fiber. Wireless local-area networks (LANs) are benefiting from spread-spectrum technology, just as cellular telephony is. Also planned is provision of satellite-based, global mobile voice and datacom services to pocketsized, hand-held devices     

Transhybrid loss with RC balance circuits for primary-rateISDN transmission systems

The authors report a method for the reduction of the near-end echo in the subscriber loop environment for primary-rate ISDN full-duplex data transmission. The technique uses an RC network as the matching input line impedance at the transmitter to reduce the near-end echo. Data rates ranging from the ISDN basic rate with (2B+D) channels to primary rate with (23B+D) channels are covered. The results indicate that a single basic configuration for the balancing line impedance may be adapted to keep the transhybrid loss in the range of about 22 dB in the worst case over the entire frequency range of interest. The balancing procedure for the hybrid takes place in a training sequence during which the component values of the RC matching circuit are adjusted from their initial values by an iterative adaptation procedure. Two techniques for optimizing the component values have been verified. For all cases examined, including worst-case line configurations, the components of the RC matching circuit have converged to final values, for which the minimum transhybrid loss had a maximum above 20 dB     

Gigabit single-mode fiber transmission using 1.3-µm edge-emitting LEDs for broad-band subscriber loops

This paper describes gigabit single-mode fiber transmission using 1.3-μm edge-emitting LED's for broad-band subscriber loops, focusing on a method of calculation for maximum transmission distance and 1.2-Gbit/s and 600-Mbit/s transmission experiments. Gigabit single-mode fiber transmission is necessary for subscriber loops, especially in broad-band ISDN and optical CATV systems. Edgeemitting LED's are excellent light sources because of their high power launched into the fiber compared with surface-emitting LED's, and currently lower cost and higher reliability than laser diodes. The maximum transmission distance is carefully estimated by taking into account the wavelength dependence for both chromatic dispersion and loss of the single-mode fiber, and the possibility of gigabit transmission near the dispersion free wavelength 1.3 μm, is confirmed. Encouraged by the above results, we demonstrate 1.2-Gbi,t/s 10-km and 600-Mbit/s 20-km transmission experiments using a newly developed 1.3-μm edge-emitting LED and a new driver circuit with a simple response compensation circuit. These results show the proposed calculation method and the LED response compensation circuit to be powerful tools for the realization of low-cost gigabit single-mode fiber transmission using edge-emitting LED's.